1. Field of the Invention
The invention relates to furnaces comprising a plurality of heat pipes and more particularly to a control to detect a malfunction of any of the heat pipes.
2. Description of the Background Art
Heat pipe furnaces typically comprise a plurality of heat pipes for transferring heat energy from a heat source, for example air heated by a burner, to a medium to be heated, for example conditioned air circulated throughout a building.
A heat pipe comprises a sealed tubed containing a vaporizable fluid formed of a horizontal evaporator section and an upwardly inclined condenser section sealingly connected thereto.
The evaporator sections of the heat pipes are sequentially located in the proximity of the heated air, and the heated air passes thereover.
Heat energy in the heated air is removed by the evaporator sections, causing the vaporizable fluid in the evaporator sections to vaporize. The vapor then travels upwardly into the condenser section.
The condenser sections of the heat pipes are located in the proximity of the conditioned air, and the conditioned air passes over the condenser sections. The vapor therein is condensed to fluid upon the release of the heat energy therefrom to the conditioned air. Once condensed, gravity causes the fluid to return to the evaporator sections where the fluid will again be vaporized in a cyclical manner.
Individual heat pipes are subject to malfunctions. For example, a leak can cause the heat pipe to lose fluid. Moreover, a vapor lock can occur wherein a vapor bubble forms in the heat pipe preventing the cyclic flow of the fluid. Such a malfunction will cause the evaporator section not to remove sufficient heat energy from the heated air and, hence, will cause the associated condensing portion to function at an abnormally low temperature. As a result, furnace efficiency decreases and further damage to the malfunctioning heat pipe can occur.
One method of detecting the malfunction of one of the heat pipes has been to individually monitor the operating temperature of each of the heat pipes. However, such individual monitoring adds to the overall cost of the furnace and adds to the furnace additional items having a potential to fail.